The present invention relates generally to a new engine for use in, for example, personal watercraft. In particular, the present invention relates to a new four-stroke in-line engine that was developed with a view to the future stricter environmental and emission regulations. The engine has an improved valve train arrangement for a lower engine profile and easy access to the spark plug assembly.
There is a very popular type of watercraft known as a xe2x80x9cpersonal watercraftxe2x80x9d which is designed to be operated primarily by a single rider. Although this type of watercraft is commonly employed for single riders, frequently provisions are made for accommodating additional passengers although the maximum number of passengers is more limited than conventional types of watercraft.
This type of watercraft is also generally quite sporting in nature and normally accommodates at least the rider on a type of seat in which the rider sits in a straddle fashion. The passenger""s area is frequently open through the rear of the watercraft so as to facilitate entry and exit of the rider and passengers to the body of water in which the watercraft is operating, as this type of watercraft is normally ridden with passengers that are wearing swimming suits.
These personal watercraft are generally quite small so that they can be conveniently transported from the owner""s home to a body of water for its use. Because of the small size, the layout of the components is extremely critical, and this gives rise to several design considerations that are peculiar to this type of watercraft. However, due to its sporting nature it is also desirable if the watercraft is powered by an engine and propulsion device that are not only efficient but also generate sufficient power.
Traditionally, two-cycle engines have been used to power watercraft, including personal watercraft. These engines have the advantage that they are fairly powerful, relatively lightweight, and compact.
One particular disadvantage to the two-cycle engine is its emission content. Two-cycle engines generally exhaust larger quantities of hydrocarbons and other pollutants than four-cycle engines due to cylinder charging inefficiencies and the combustion of lubricating oil among other things. When measures are taken to reduce emissions of the two-cycle engine, other generally undesirable consequences can result, such as an increase in the weight of the engine, a reduction of its power output or the like. With concern for the environment and increasingly strict emissions requirements being instituted by various governing bodies. There is motivation to provide a power plant that reduces exhaust emissions while retaining other advantageous characteristics such as compactness, low weight and high power output.
Four-cycle engines are commonly used as power plants in other applications, such as automobiles. These engines have the advantage that their emissions output are generally desirably lower as compared to a two-cycle engine for a given power output. These engines, however, are considerably larger than two-cycle engines and therefor present difficulties when locating the engine in a personal watercraft. It is desirable to provide an engine with a reduced profile. This may be accomplished with proper configuration of the valve train arrangement and cylinder head.
U.S. Pat. No. 4,267,811 to Springer, entitled xe2x80x9cCylinder Head For a Mixture-Compressing Internal Combustion Engine,xe2x80x9d U.S. Pat. No. 4,553,515 to King et al., entitled xe2x80x9cCylinder Head For Spark Ignition Internal Combustion Engine,xe2x80x9d U.S. Pat. No. 4,662,323 to Moriya, entitled xe2x80x9cOverhead Cam Type Valve Actuating Apparatus For Internal Combustion Engine,xe2x80x9d U.S. Pat. No. 4,741,302 to Oda et al., entitled xe2x80x9cInternal Combustion Engine,xe2x80x9d U.S. Pat. No. 4,773,361 to Toki et al., entitled xe2x80x9cOverhead Cam Type Four-Valve Actuating Apparatus For Internal Combustion Engine,xe2x80x9d U.S. Pat. No. 4,796,574 to Fujii et al., entitled xe2x80x9cSOHC Type Internal Combustion Engine,xe2x80x9d U.S. Pat. No. 5,009,204 to Ishii, entitled xe2x80x9cSpark Plug Arrangement In An Overhead Camshaft Engine,xe2x80x9d U.S. Pat. No. 5,095,859 to Iwata et al., entitled xe2x80x9cSOHC Type Internal Combustion Engine,xe2x80x9d U.S. Pat. No. 5,513,606 to Shibata, entitled xe2x80x9cMarine Propulsion Unit,xe2x80x9d U.S. Pat. No. 5,829,402 to Takahashi et al., entitled xe2x80x9cInduction System For Engine,xe2x80x9d U.S. Pat. No. 5,839,930 to Nanami et al., entitled xe2x80x9cEngine Lubricating System For Watercraft,xe2x80x9d and U.S. Pat. No. 5,846,102 to Nitta et al., entitled xe2x80x9cFour-Cycle Engine For A Small Jet Boatxe2x80x9d disclose various valve train arrangements for an internal combustion engine. Each discloses positioning the intake and exhaust valves at an angle within the cylinder head. Rocker arm assemblies are used to actuate the valves. None of these references, however, disclose using a single rocker arm having a pair of operating arms to operate a pair of valves such that the spark plug assembly is located between the operating arms of the rocker arm. Furthermore, none of these references provides a spark plug assembly that permits easy removal of the spark plug while protecting the same from the elements.
It is an object of the present invention to provide a four stroke, in-line engine having a compact construction.
It is another object of the present invention to provide a four stroke, in-line engine having a modular construction to permit the interchange of parts between various engine models.
It is another object of the present invention to provide a four stroke, in-line engine having improved exhaust emission characteristics.
It is another object of the present invention to provide a four stroke engine having a narrow and low profile.
It is another object of the present invention to provide a four stroke engine having a low profile valve actuation assembly for controlling the operation of the intake and exhaust valves.
It is another object of the present invention to provide a cylinder head having a low profile to reduce engine height.
It is another object of the present invention to offset the placement of the intake valves and exhaust valves with respect to a vertical axis within the cylinder head to reduce engine height.
It is another object of the present invention to provide an improved spark plug mounting assembly for easy access within the cylinder head.
It is another object of the present invention to provide a Y-shaped intake rocker arm assembly providing compact construction.
It is yet another object of the present invention to provide a four stroke engine having an improved oil collection system and oil holding tank.
It is another object to provide a four stroke engine which combines a closed loop cooling system and an open loop cooling system for enhanced cooling of the engine in accordance with the present invention.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open loop cooling system enhances cooling of the crankcase and cylinder head.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open cooling system lowers the temperature of the exhaust manifold such that the exhaust manifold functions as a heat sink for the crankcase and cylinder head.
It is another object of the present invention to provide a closed loop cooling system for selectively cooling the crankcase and cylinder head of the four stroke engine.
It is another object of the present invention to provide a closed loop cooling system having a selectively operable heat exchanger.
It is another object of the present invention to provide a supercharger for enhanced engine performance.
In accordance with the present invention, a four stroke internal combustion engine is disclosed. In the preferred form, the engine includes a crankcase having a crank shaft rotatably mounted therein. A cylinder head is connected to the crankcase. The crankcase and the cylinder head together form at least one cylinder. Each cylinder has at least one intake valve and at least one exhaust valve a crankshaft rotatably mounted within the crankcase. A valve actuation assembly operates the intake valves and the exhaust valves. The valve actuation assembly is located in the cylinder head between the intake valve axis and the exhaust valve axis.
In accordance with the present invention, the valve actuation assembly includes a cam shaft that is rotatably mounted within the cylinder head. It is preferable that the cam shaft is operatively coupled to the crank shaft such that rotational movement of the crankshaft is transferred to the cam shaft. A support axle is mounted within the cylinder head and offset from the cam shaft. The support axle has a central passageway. The valve actuation assembly includes at least one exhaust rocker arm is pivotally mounted within the cylinder head on the support axle. Each exhaust rocker arm is operatively coupled to the cam shaft for operating the exhaust valves. The valve actuation assembly also includes at least one intake rocker arm is also pivotally mounted within the cylinder head on the support axle. Each intake rocker arm is operatively coupled to the cam shaft for operating the intake valves.
In accordance with the present invention, the engine further includes a lubrication system for lubricating the engine. The lubrication system includes a supply of lubricant to the cylinder head. A portion of the supply of lubricant flows through the central passageway in the support axle.
In order to reduce the overall profile of the engine and provide sufficient space a spark plug assembly and the necessary crank gear to cam gear ratio, the intake valves and exhaust valves are disposed at an angle with respect to the longitudinal axis of the cylinder. To accomplish this, the cam shaft and the support axle are also offset with respect to the longitudinal axis. At least one of the cam shaft and the support axle are positioned closer to the exhaust valves than the intake valves. It is contemplated that the longitudinal axis of the spark plug assembly extends substantially parallel to the longitudinal axis of the intake valves. It is also contemplated that the longitudinal axis of the spark plug assembly and the intake valve axis may form an acute angle not greater than 20xc2x0.
In accordance with the present invention, each exhaust rocker arm includes a cam follower located on one end of the exhaust rocker arm. The cam follower is adapted to follow a profile of an exhaust cam lobe located on the camshaft to operate the exhaust valves. An exhaust hydraulic adjuster located on an opposite end of the exhaust rocker arm. Each exhaust rocker adjuster includes a slidable piston assembly that is adapted to contact and operate the exhaust valve in response to movement of the exhaust rocker arm by the exhaust cam lobe. A fluid passageway extends from the piston assembly through the exhaust rocker arm to the support axle. Fluid in the central passageway in the support axle flows through the fluid passageway to bias the piston assembly into engagement with the exhaust valve.
In accordance with the present invention, the valve actuation assembly includes an intake rocker arm for operating a pair of intake valves. Like the exhaust rocker arm, each intake rocker arm includes a cam follower located on one end of the intake rocker arm. Unlike the exhaust rocker arm, the intake rocker arm includes a first actuator arm for operating a first intake valve, and a second actuator arm for operating a second intake valve. Each actuator arm includes a slidable piston assembly, as described above. The cam follower and actuator arms have a generally Y-shape.
In accordance with the present invention, the exhaust rocker arms are rotatably mounted on the support axle on opposite sides of the intake rocker arm. A spark plug assembly is positioned on the cylinder head between the first actuator arm and the second actuator arm.
The spark plug assembly includes a tube assembly secured to the cylinder head. The tube assembly may be plastic. A spark plug connector is removably located within the tube assembly. The spark plug connector may include a splash cover to prevent contaminants from entering the spark plug assembly. A spark plug is secured to the spark plug connector.
The present invention is also directed to a personal watercraft for at least one passenger having an internal combustion engine secured to the hull below a seating assembly. The internal combustion engine includes a valve actuation assembly, as described above and described in greater detail below.